The spinal column is a highly complex system of bones and connective tissues that provide support for the body and protect the delicate spinal cord and nerves. The spinal column includes a series of vertebral bodies stacked one atop the other, each vertebral body including an inner or central portion of relatively weak cancellous bone and an outer portion of relatively strong cortical bone. Situated between each vertebral body is an intervertebral disc that cushions and dampens compressive forces exerted upon the spinal column. A vertebral canal containing the spinal cord is located behind the vertebral bodies.
There are many types of spinal column disorders including scoliosis (abnormal lateral curvature of the spine), excess kyphosis (abnormal forward curvature of the spine), excess lordosis (abnormal backward curvature of the spine), spondylolisthesis (forward displacement of one vertebra over another), and other disorders caused by abnormalities, disease or trauma, such as ruptured or slipped discs, degenerative disc disease, fractured vertebrae, and the like. Patients that suffer from such conditions usually experience extreme and debilitating pain as well as diminished nerve function.
Neurophysiologic monitoring has become an increasingly important adjunct to surgical procedures where neural tissue may be at risk. Spinal surgery, in particular, involves working close to delicate tissue in and surrounding the spine, which can be damaged in any number of different ways. When spinal cord monitoring is required, somatosensory evoked potential (SSEP) monitoring is often chosen. SSEP monitoring traditionally involves complex analysis and specially trained neurophysiologists are generally called upon to perform the monitoring. Even though performed by specialists, interpreting the complex waveforms in this fashion is nonetheless disadvantageously prone to human error and can be disadvantageously time consuming, adding to the duration of the operation and translating into increased healthcare costs. Even more costly is the fact that the neurophysiologist is required in addition to the actual surgeon performing the spinal operation. Past developments have attempted to solve these challenges in various ways. One such development is so-called automated or surgeon-driven SSEPs monitoring.
For some time, surgeon-driven and traditional neuromonitoring systems have co-existed and have experienced some of the same challenges in performing intraoperative neuromonitoring. One such challenge is that neurophysiologic signals are typically sub-microvolt evoked potentials that are hard to resolve in an “electrically hostile” environment such as an operating room. What is needed are systems and methods for improved SSEP data acquisition that provides meaningful data to user. According to a broad aspect of the present invention, there are provided methods and techniques to enhance, facilitate, and/or simplify the process of detecting neurophysiologic signals (e.g. SSEP signals) particularly in the presence of noise including ambient electrical activity and non-evoked biopotentials.